Cathode arrangement



Oct. 17, 1933. NE K 1,930,704

CATHODE. ARRANGEMENT Fil'edflct. 17, 1929 2 sheets-sheet 1 Oct 17, 1933. W|ENEKE 1,930,704

CATHODE ARRANGEMENT M a C Fj 4. d e g Jm/emars Q7514 ZWW.

Patented Oct. 17, 1933 umrso STATES CATHODE ARRANGEMENT Bruno Wienecke, Berlin, Germany Application October 17, 1929, Serial No. 400,428, and in Germany October 17, 1928 4 Claims.

It has been proposed to connect the two ends of the cathodes of electron valves heated by alternating current to the A. C. source across a potentiometer and to tap the middle of such potentiometer for the purpose of connecting the grid potential and closing the plate circuit. By itself any point of such potentiometer or of the secondary winding of a transformer may, for

. instance, by grounding be provided with a fixed potential.

. of the plate current.

The connection in the middle of the potentiometer, however, has the great advantage that,.while the A. 0. potential may produce a varying distribution of the emitting length of the filament in the vacuum vessel, the entire emission current which, for instance with negative grid bias, reaches the anode, is not varied by the fluctuation of the potential. If, in consequence of the reduction of the plate potential at a certain moment, a reduction of the plate since in such case operations are carried onrin systems.

' the straight part of the characteristic.

In multiple system valves or multiple valves this rule may be applied without diiiiculty if the different filaments are connected in parallel.

. For connecting the grid and closing the plate circuit the position of the electric centre is secured by central tapping of the potentiometer. In very cases it is, however, not advisable to connect in parallel the filaments of different This is more particularly not advisable if the cathodes are of entirely different kinds and if some of them belong, for example, to an output stage and the others to a voltage amplification system. In that case special resistance would be necessary for the distribution of current, as in consideration of the construction the resistances of the cathodes to be connected in parallel cannot be varied at will.

If 2 or more cathodes for multiple system valves or multiple valves are connected in serice and if at the two ends of such heating circuit the external A. C. source is to be connected, for instance, across a transformer, the electriccentre for every single cathode can no longer be secured in position by a single tap on the transformer winding or on the potentiometer connected in parallel. For this reason it has heretofore beenimpossible in such valves with cathodes heated with A. C. current to avoid heating and anode hum.

The invention relates to a method of removing these evils. According to the invention those points or" a potentiometerwhich have the same potential as the centre of the individual cathodes are branched ofi for the connection of the plate circuits or grids. What that means in practice, is explained by way of an exemplary construction.

The invention willbe more fully understood from the accompanying drawings in Figure l of which is illustrated a diagram for an electrode valve-with two electrode systems and the coupling elements.

' Fig.2 shows a diagramfwherein according to the invention to the ends of a potentiometer here are joined the two halves of the one cathode which in turn are connected with one another by the other cathode.

Fig. 3 shows an arrangement, wherein the several parts of the cathodes of the two systems are connected up in series, the most sensitive of said cathodes being placed in the centre.

Fig, l shows as a further exemplary embodiment the arrangement in the case of three electrode systems.

In Fig. 1 the diagram is shown for an electrode valve with two electrode systems and the coupling element built in; 1, 2 are the two cathodes, 3, 4 the two grids, 5, 6 the two anodes,

7 the plate resistance, 8 the grid blocking condenser and 9 the grid leak resistance. The filament voltage for'the two cathodes 1 and 2, connected in series, is taken from th potentiometer 11 across atransiormer 10. The potentiometer 11 has two tappings Whose potential corresponds to the electric centre of the two cathodes 1 and 2.

This arrangement necessitates two separate current sources 12 and 13, and, if grid potential batteries are provided for at all, two separate grid voltage batteries. 14 and 15. The circuit is completed by a telephone or loudspeaker 16.

This separate arrangement of the-grids and. plate batteries makes it possible .that by two tappings the electric grids of the cathodes 1 and'2 are fixed to an only potentiometer 11.

The invention is by no means limited to this arrangement. In many cases it is difiicult to obtain separate sources of E. M. According to the invention there is the possibility too of fixing the electriccentres of two and even more 110 cathodes in such manner that for all systems only one plate battery and only one grid voltage battery is required. To that end the cathodes for the several systems are, according to the invention, connected in series in such manner that, starting from the two ends of the heating line joined to the outer current source one half each of the cathodes forming part of an electrode system are arranged in possibly equal distance. Such arrangement is, by way of example, shown in the diagram of Fig. 2. In that figure 11 is the potentiometer which according to the arrangement in Fig. 1 consists of an ohmic resistance. In the place of such ohmic resistance tapped in the centre two equally large resistances may be used. There further no objection to using condensers, for instance a differential twin condenser or two separate condensers of equal size in the place of the ohmic resistances for the potentiometer.

To the ends of the potentiometer the two halves of the cathode 2 are joined which in turn are connected with one another by the cathode 1.

The potentiometer 11 being now tapped exactly in the centre and if at this tap the outer plate and grid circuit are closed, the result is that not only is the electric centre of the oathode 1 exactly secured in position and a heating and anode hum in such system removed, but the electric centres of the cathode halves 2, 2 are also secured in position and disturbing subsidiary noises removed in like manner. .It is necessary and sufficient for this purpose that the two cathode halves 2, 2 are assigned to the same electrode systems. This is illustrated in Fig. 3. Corresponding to the references of Figs. 1 and 2, 1 in Fig. 3 is the cathode of an electrode system, for instance, the voltage amplification system of a multiple valve, while 2, 2 are the two halves of the cathode of the output stage. The electrode system appertaining to the cathode 1 consists of the grid 3 and the anode 5. while the electrode system with grid 4 the anode 6 appertains to the two cathode halves 2, 2. 7

If the two branches of the heating line have the same resistance, the centre of the cathode 1 has the same potential as the centre of the potentiometer 11. An alternating potential applied to the potentiometer 11 thus generates at a certain moment at the one end a potential which, for example, is by just as much positive with respect to the centre of the cathode .1, as the potential at the other end is negative with respect to said centre of the cathode 1. If we now proceed from both ends of the potentiometer 11 on both branches with the same speed towards the centre, we always obtain pairs of points of the same potential with opposite signs. Such points are, for instance, the two lower ends of the cathode halves 2, 2. In accordance with the above specification We obtain with the two cathode halves 2, 2 the same conditions, as with cathode 1 or generally with every cathode tapped in the centre. At every moment, notwithstanding the alternating potential at the potentiometer 11 we obtain no fluctuation of the emission current, but only according to the distribution of potential a different distribution of the electron cloud along the cathode. If, for example, in a definite moment the potential at the lower end of the l half of the cathode is higher by a certain Viv amount and the control voltage is lower by the same amount, then in the same moment the potential at the lower end of the right half of cathode 2 is lower by the amount and the control voltage higher, the whole of the electrons controlled thus remaining the same.

As the fixation of the electric centre for the central cathode, i. e. cathode 1, can according to the exemplary construction of Fig. 2 and Fig. 3 be most accurately made, the arrangement is empirically made in such manner that the most sensitive cathode is placed in the centre. In an amplifier consisting of several cascades the most sensitive amplifier stage is always the first cascade and for that reason the cathode of that electrode system is placed in the middle of the heating circuit end the cathode halves in each branch follow each other from the middle in. the same order as the cascades.

This arrangement results in a furth r great advantage. In multiple valves with electrode systems of diiierent kinds it makes to a great extentallowance for the different consumption of filament power. If such multiple valve consists of voltage amplifying stages and an output stage, a larger number of filaments connected in parallel is generally found necessary for the latter stage. With the circuit according to the invention a subdivision into two filaments takes place of itself. For the two cathode halves 2, 2 in 2 and 3 generally long thin filaments will be used the result being a large drop of potential between the ends of these cathodes and therefore with given current a large power. The cathode 1 for the voltage amplification system may consist of a single filament which should best be thick and short in order that for the same reason the filament power for this system is a low one.

The filament 1 may, for example, also be of a V-shape and may be suspended at the central points of a spring. There is also no objection to the two cathode halves being again subdivided in several, vfor example 2, 3, 4 or even more, threads connected in parallel.

The invention is, moreover, by no means limited to the connection in series of two cathodes. 3 and even more cathodes may just as well according to the invention be connected in series. Fig. 4"shows as such further exemplary .constructions the arrangement in the case of three electrode systems. The cathode a of the electrode system I is arranged in the centreof the heating circuit. From the centre the two halves b and c of the electrode system II and then the two cathode halves d and e of theelectrode system III are following. .The latter are directly joined to the two ends 1 and g of the potentiometer 11. According to the invention the heating circuit passes from 1 across d to b up to the centre of a. This is one branch of the heating circuit; the other branch passes from the other half of 11. across 0 and e to g. a

The local arrangement of the difierent electrode system may be effected in the most difierent manners. According to the known principles in the construction of the multiple valves the arrangement is made such that, as far as possible, injurious line capacities are avoided and that the systems influence each other mutually as little as possible.

I claim:

1'. In an amplification system a plurality of electron discharge devices, each of said devices having grid and plate electrodes, one common cathode circuit for all said devices, said cathode circuit being subdivided in more than two parts and each of said devices containing two parts of said subdivided cathode circuit, the two midparts being equal sections of a single cathode each two parts being symmetrical relative to the electrical mid-point of said cathode circuit, a transformer connected with a source of alternating current and having its secondary connected with said cathode for heating it to incandescence, a potentiometer connected across said secondary, means to connect said grids and plates with a mid-point on said potentiometer, and means for coupling said electron discharge devices with one another and with the input and output circuit.

2. In an amplification system a plurality of electron discharge devices, each of said devices having grid and plate electrodes, one common cathode circuit for all said devices, said cathode circuit being subdivided in more than two parts and each of said devices containing two parts of said subdivided cathode circuit, the two midparts being equal sections of a single cathode, each two parts being symmetrical relative to the electrical mid-point of said cathode circuit, at which the most sensitive electrode system contains the two mid-parts of the common cathode which may be joint to one sole part, a transformer connected with a source of alternating current and having its secondary connected with said cathode for heating it to incandescence, a potentiometer connected across said secondary, means to connect said grids and plates with a mid-point on said potentiometer, and means for coupling said electron discharge devices with one another and with the input and output circuit.

3. In an amplification system a voltage amplifying stage device and an output stage device, each of said devices having grid and plate electrodes, one common cathode circuit for both devices, said cathode circuit being subdivided and each of said devices containing two parts of said subdivided cathode circuit, each two parts being symmetrical relative to the electrical midpoint of said cathode circuit, said voltage amplifying stage device containing the two midparts of the cathode being equal sections of a single cathode, a transformer connected with a source of alternating current and having its secondary connected with said cathode circuit for heating it to incandescence, a potentiometer connected across said secondary, means to connect said grids and plates with a mid-point on said potentiometer, and means for coupling said electron discharge devices with one another and with the input and output circuit.

4. In a amplification system a voltage amplifying stage device and an output stage device, each of said devices having grid and plate electrodes, one common cathode circuit for both devices, said cathode circuit being subdivided and each of said devices containing two parts of said subdivided cathode circuit, each two parts being symmetrical relative to the electrical midpoint of said cathode circuit, said voltage amplifying stage device containing the two mid-parts of the cathode being equal'sections of a single cathode and the output stage device containing two equal parts, each part being once more subdivided in several threads connected in parallel, a transformer connected with a source of alternating current and having its secondary connected with said cathode circuit for heating it to incandescence, a potentiometer connected across said secondary, means to connect said grids and plates with a mid-point on said potentiometer, and means for coupling said electron discharge devices With one another and with the input and output circuit. 

